1. Technical Field
This invention relates to the field of printing press apparatus for automatically printing a web of material and, more particularly, to a printing press including an endless belt having at least one associated printing station.
2. Description of the Relevant Art
In the art of manufacturing continuous, multi-part business forms, printing newspaper or even wallpaper and in the printing press art in general, a major shortcoming is that the size of the print pattern is limited to the size, i.e., the diameter, of the printing cylinder. As a result, printing cylinders must be changed often in order to accommodate various lengths or repeats in the desired work product.
According to one embodiment of our invention, represented by U.S. Pat. No. 4,827,315, the printing cylinder has an indeterminate length in the sense that it is able to print at any desired length or pattern repeat without the necessity of changing cylinders. In this respect, the cylinder surface may be regarded as a constantly moving surface, miles long, rather than any fixed size. This is because an ionized beam is projected onto the cylinder to create an image thereon which is transferred to a continuously moving web. As the cylinder revolves past the printing position, the image is erased and another image is formed, so as to present a constantly changing image to the web for continuous printing independent of cylinder size.
More specifically, the drum or print cylinder is provided with an image receiving photoconductor surface which is rotated past a charging or projection station where laser beams are utilized to project images on the cylinder surface. This is accomplished using laser printing technology such as that disclosed in U.S. Pat. No. 3,836,917. This cylinder is then rotated to a development station where a powder or toner is selectively deposited on only the charged image areas. When a plurality of colors are used for a particular business forms application, as many as four or more cylinders are employed, each applying a single color.
After the image is transferred to the web, the sheet or web is passed through heating and chilling sections to fix the toner or powder on the web.
Meanwhile, immediately after the images from the respective cylinders are transferred onto the web, the images are erased, again with the aid of laser beams which discharge the photoconductive surfaces of the respective cylinders.
Upon passing through the various printing stations, the web is fed through a standard punch ring to an image scanner. At this station, the printed image may be reproduced, again with the aid of laser beams, and converted to digital form and stored in the computer. Conventional feedback techniques are then employed to correct and/or improve specific areas of the form, or to make minor changes in the form format.
The web thereafter passes through laser operated punch heads and cross-perforation devices and is subsequently wound on a rewind roll.
It is to be understood that computer technology is employed to program the press to produce the desired printing, color application and so on at each of the printing stations. In a preferred embodiment, controls to the press as well as printing information are included in diskette or cassette form.
The press as described hereinabove has several attendant advantages. The overall weight of the press is substantially reduced, alleviating problems of readjustment and realignment due to distortion of heavy frame members and compression of floor contours.
The press as described hereinabove enjoys reduced power consumption since large motors (e.g., 7.5 hp) are utilized only to draw the paper through the press, with smaller additional motors (adding perhaps another 4 or 5 hp) used in the individual subsystems. This is to be compared with conventional prior art printing presses which normally use in excess of 50-60 hp.
The press as described hereinabove eliminates the use of conventional negatives and plates, along with the necessary chemicals. The computerization of all controls also eliminates the need for numbering machines and problems associated therewith. Our related copending U.S. application Ser. No. 281,062 filed Dec. 7, 1988, incorporated herein by reference, describes a controlled method and apparatus for automatic numbering of forms on a rotating printing press.
The immediate drying of the ink at the respective printing stations eliminates the necessity of conventional infrared and ultraviolet dryers.
Conventional makeready procedures are also radically altered. With the press according to this invention, the operator need only install a fresh roll of paper in the press, remove the finished roll, and select the appropriate program for manufacturing a business form of the desired size and format.
It may be further appreciated that even the loading and unloading of the paper rolls themselves may be automated to even further reduce the already minimized manual labor associated with press operation.
In the art of photocopying, it is recognized that so-called endless belts may be provided in which at least one cylinder is used to drive the belt. The belt is less expensive to manufacture than a cylinder and may be inexpensively and easily replaced when broken or when a coating affixed to the belt deteriorates to the point when it is no longer useful. For example, the following U.S. patents assigned to Ricoh Company, Ltd. of Japan are exemplary of endless belt apparatus: U.S. Pat. Nos. 4,668,072, 4,674,858, 4,751,549, 4,758,486 and 4,772,253. In particular, U.S. Pat. No. 4,772,258 incorporated herein by reference discloses a typical wide seamless, endless belt of sheet metal lined with flexible material on one side and having another side used as a substrate for electrostatic copying.
In summary, then, while a cylinder may provide a printing surface of indeterminate length, a cylinder is expensive to replace. Consequently, there remains a requirement in the art to provide an endless belt type of printing press, the endless belt of which, for example, may be adapted for printing applications from the copying arts.